Connect Postgres for FastAPI

Summary

Connect a FastAPI app to PostgreSQL on Ample. Read DATABASE_URL at runtime with psycopg: when you supply one with --env it is delivered encrypted and takes precedence; when you supply none and the app needs PostgreSQL, Ample auto-provisions a managed PostgreSQL 16 database and injects its connection string.

Representative Queries

• Connect Postgres for FastAPI
• Where can I host Connect Postgres built with FastAPI?
• I need driver setup, connection settings, secret handling and a real connection test.

Prerequisites

• psycopg reading the DATABASE_URL environment variable at runtime
• Either a production DATABASE_URL to pass with --env, or nothing (auto-provision)
• An Ample account token with servers:write and databases:read

Workflow Steps

1. Read the URL at runtime
   Open connections from the DATABASE_URL environment variable inside the app; never commit credentials and never connect at build time.

2. Choose the source of the database
   Pass --env DATABASE_URL=... for an existing database, or omit it to let Ample provision a managed one on first deploy and reuse it on redeploys.

   Command: ample deploy . --name --public --start "python3 run.py"

3. Test the connection through the app
   Expose a route (/items) that runs a trivial query and returns postgres=ok.

4. Verify
   Fetch the live URL and run the success checks below. On failure read the build log, then the runtime log, fix the cause and deploy again; do not blind-retry.

   Command: ample logs --kind build

Success Checks

• Database route reports a live connection:
  • Kind: http_get
  • Path: /items
  • Expect: postgres=ok

Limitations

• Verified on the node-22 template at s-1vcpu-1gb; other templates and sizes are not verified by this recipe.
• Region, compliance attestations and request-duration limits are unknown and not claimed.
• Apps auto-pause when idle and wake on the next request; always-on is an operator setting, not a plan feature.
• Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures are not verified.
• Apps and their managed databases are placed together; cross-node shared databases are unsupported.

Cost Estimate

• Currency: USD
• Monthly Amount: 10.0
• Basis: Size prices from pricing.toml (loaded by the API) at build revision 1ac5595375130d45290090e82ed0f554ccd45405-dirty

Components

• App server
  • Size: s-1vcpu-1gb
  • Quantity: 1.0
  • Monthly Amount: 5.0
• Managed PostgreSQL database
  • Size: s-1vcpu-1gb
  • Quantity: 1.0
  • Monthly Amount: 5.0

Note: Apps and managed databases auto-pause when idle; the estimate is the always-on monthly price of the tested sizes. Plan quotas and budgets apply.

Evidence Summary

• Kind: canary_run
  Summary: FastAPI REST API using psycopg with no DATABASE_URL supplied: Ample auto-provisioned a managed PostgreSQL 16 database and /items reported postgres=ok after a real insert and count.
  Observed At: 2026-09-20T01:42:25Z

• Kind: canary_run
  Summary: Node app needing PostgreSQL with no DATABASE_URL: a managed database was auto-provisioned and /db reported postgres=ok.
  Observed At: 2026-09-19T23:55:33Z

Formats

• HTML
• Markdown
• JSON